This invention relates generally to improving specific fuel consumption (SFC) of turbomachinery, and more specifically to a cover for fasteners exposed to a fluid flow.
A gas turbine engine includes a turbomachinery core having a high-pressure compressor, combustor, and high-pressure turbine in serial flow relationship. The core is operable in a known manner to generate a primary flow of propulsive gas. A typical turbofan engine adds a low-pressure turbine driven by the core exhaust gases which in turn drives a fan rotor through a shaft to generate a bypass flow of propulsive gas. In the case of a high bypass engine this provides the majority of the total engine thrust.
The fan rotor includes an array of fan blades extending radially outward from a fan disk. A spinner is connected to an aft support ring, which is connected to the fan disk, using mechanical fasteners. The spinner is used to reduce aerodynamic drag and to smooth air flow so that air enters the engine inlet more efficiently, amongst other functions. The spinner includes an array of clearance slots positioned about a periphery of the spinner to allow the mechanical fasteners to reside below an outer peripheral surface of the spinner. The spinner also includes an array of trim pockets positioned about the periphery to permit trim bolts to be placed therein. The trim bolts are used to provide a final correction or offset of an imbalance.
Together, the mechanical fasteners, trim bolts, clearance slots, and trim pockets create a three-dimensional (3D) feature that resides in the aero flow path. This 3D feature affects the laminar flow of the inlet air which in turn affects the performance. Thus, there is a need for a cover that reduces the size of the 3D feature, helps smooth the air flow, reduces local flow losses, and improves the specific fuel consumption (SFC) of the turbomachinery.